Numerical simulation of earth-air heat exchanger application for Indonesian simple house air conditioning system

Research on an air-conditioning (AC) system that uses soil as a heat storage is still not widely conducted in Indonesia. The soil functions as a hot or cold storage medium by flowing fresh air through a heat exchanger due to its constant temperature tendency throughout a year. Earth-air exchanger (EAHE) application was simulated and got the results that soil with a volume of 12 m3 is potentially used as a heat exchange medium with a heat transfer surface area of 24.4 m2. The EAHE cooling capacity obtained is 1,002–1,282 watts depending on soil condition. Increasing the pipe diameter and airflow velocity decreases the average temperature difference by 42.9% per inch and 47.2% per m/s, respectively. Meanwhile, increasing the pipe thickness and soil depth increases the average temperature difference by 1.59% per millimeter and 6.06% per meter, respectively. The pipe interface distance recommended is greater than or equal to 200 mm. The EAHE can meet the Indonesian National Standard thermal comfort standard and ASHRAE breathing zone outdoor airflow for ventilation standard but can only meet 23.5%–30.0% of simple house-cooling loads. It consumes 75.8% lower energy and has an 139%–230% higher coefficient of performance than a split AC system.